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C++ named requirements: UnformattedInputFunction - cppreference.com

[edit] Requirements

An UnformattedInputFunction is a stream input function that performs the following:

1)

Constructs an object of type

basic_istream::sentry

with automatic storage duration and with the

noskipws

argument set to

true

, which performs the following:

If eofbit or badbit are set on the input stream, sets the failbit as well, and if exceptions on failbit are enabled in this input stream's exception mask ((exceptions() & failbit) != 0), throws ios_base::failure.
Flushes the tie()'d output stream, if applicable.

2)

Checks the status of the sentry by calling

sentry::operator bool()

, which is equivalent to

basic_ios::good

If the operator returns false or sentry's constructor throws an exception:

Sets the number of extracted characters (gcount) in the input stream to zero.
If the function was called to write to an array of CharT, writes CharT() (the null character) to the first location of the array.

If the operator returns true, performs the input as if by calling rdbuf()->sbumpc() or rdbuf()->sgetc().

If the end of the stream is reached (the call to rdbuf()->sbumpc() or rdbuf()->sgetc() returns Traits::eof()), sets eofbit. If exceptions on eofbit are enabled in this stream's exception mask ((exceptions() & eofbit) != 0), throws ios_base::failure.
If an exception is thrown during input, sets badbit in the input stream. If exceptions on badbit are enabled in this stream's exception mask ((exceptions() & badbit) != 0), the exception is also rethrown.

Exceptions thrown from basic_ios::clear are not caught or rethrown.

If no exception was thrown during input, sets the number of extracted characters (gcount) in the input stream.

3) In any event, whether terminating by exception or returning, the sentry's destructor is called before leaving this function.

[edit] Standard library

The following standard library functions are UnformattedInputFunctions.

std::getline, except that it does not modify gcount.
basic_istream::operator>>(basic_streambuf*)
basic_istream::get
basic_istream::getline
basic_istream::ignore
basic_istream::peek
basic_istream::read
basic_istream::readsome
basic_istream::putback, except that it first clears eofbit
basic_istream::unget, except that it first clears eofbit
basic_istream::sync, except that it does not modify gcount
basic_istream::tellg, except that it does not modify gcount
basic_istream::seekg, except that it first clears eofbit and does not modify gcount
std::ws, except that it does not modify gcount

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR Applied to Behavior as published Correct behavior LWG 61 C++98 it was unclear whether throwing an exception because of
setting eofbit and/or failbit will result in setting badbit exceptions thrown from basic_ios::clear
are not caught or rethrown LWG 160 C++98 the process of determining whether the exception caught
is rethrown mentioned a non-existing function exception() corrected to exceptions() LWG 243 C++98 the behavior when sentry::operator bool() returns false
or the sentry object fails to be constructed was not specified specified

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